how to remove broken drill bit?

Disabled, but still do some jobs for myself...
I have a McKeller MCKM 14 hamer/chissel drill
The broken drill 'Bit' remains in the 'Slide Release' style chuck
How can I get it out please?
The Chuck (drive shaft) is 13mm size
It has: 1010w 850 speed
It is 2/3 year old and only used twice!
That fatal time, many months back - left in shed as one of 'those jobs' never to be done... - Was New from 'Focus' but now out of business!
I now need to use it.
Have had the gear box apart; but No where to use a drift, bit moves about 10mm but a burr where it broke is why it is retaining the broken drill, its too low to get hold of!
What can I do - please?